/Engine/Plugins/Experimental/PCG/Source/PCG/Public/Metadata/PCGMetadata.h
Advanced method. In a MT context, we might not want to add the entry directly (because of write lock). Call this to generate an unique index in the MT context And call AddDelayedEntries at the end when you want to add all the entries. Make sure to not call AddEntry in a different thread or even in the same thread if you use this function, or it will change all the indexes.
int64 AddEntryPlaceholder()